Argon is a chemical element with symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in the Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abundant as water vapor (which averages about 4000 ppmv, but varies greatly), 23 times as abundant as carbon dioxide (400 ppmv), and more than 500 times as abundant as neon (18 ppmv). Argon is the most abundant noble gas in Earth's crust, comprising 0.00015% of the crust.
Nearly all of the argon in the Earth's atmosphere is radiogenic argon-40, derived from the decay of potassium-40 in the Earth's crust. In the universe, argon-36 is by far the most common argon isotope, as it is the most easily produced by stellar nucleosynthesis in supernovas.
The name "argon" is derived from the Greek word ἀργόν, neuter singular form of ἀργός meaning "lazy" or "inactive", as a reference to the fact that the element undergoes almost no chemical reactions. The complete octet (eight electrons) in the outer atomic shell makes argon stable and resistant to bonding with other elements. Its triple point temperature of 83.8058 K is a defining fixed point in the International Temperature Scale of 1990.
Argon is produced industrially by the fractional distillation of liquid air. Argon is mostly used as an inert shielding gas in welding and other high-temperature industrial processes where ordinarily unreactive substances become reactive; for example, an argon atmosphere is used in graphite electric furnaces to prevent the graphite from burning. Argon is also used in incandescent, fluorescent lighting, and other gas-discharge tubes. Argon makes a distinctive blue-green gas laser. Argon is also used in fluorescent glow starters.
|Appearance||colorless gas exhibiting a lilac/violet glow when placed in an electric field|
|Standard atomic weight Ar, std(Ar)||[39.792, 39.963] conventional: 39.948|
|Argon in the periodic table|
|Atomic number (Z)||18|
|Group||group 18 (noble gases)|
|Element category||noble gas|
|Electron configuration||[Ne] 3s2 3p6|
Electrons per shell
|2, 8, 8|
|Phase at STP||gas|
|Melting point||83.81 K (−189.34 °C, −308.81 °F)|
|Boiling point||87.302 K (−185.848 °C, −302.526 °F)|
|Density (at STP)||1.784 g/L|
|when liquid (at b.p.)||1.3954 g/cm3|
|Triple point||83.8058 K, 68.89 kPa|
|Critical point||150.687 K, 4.863 MPa|
|Heat of fusion||1.18 kJ/mol|
|Heat of vaporization||6.53 kJ/mol|
|Molar heat capacity||20.85 J/(mol·K)|
|Electronegativity||Pauling scale: no data|
|Covalent radius||106±10 pm|
|Van der Waals radius||188 pm|
Spectral lines of argon
|Crystal structure|| face-centered cubic (fcc)|
|Speed of sound||323 m/s (gas, at 27 °C)|
|Thermal conductivity||17.72×10−3 W/(m·K)|
|Magnetic susceptibility||−19.6·10−6 cm3/mol|
|Discovery and first isolation||Lord Rayleigh and William Ramsay (1894)|
|Main isotopes of argon|
Ar and 38
Ar content may be as high as 2.07% and 4.3% respectively in natural samples. 40
Ar is the remainder in such cases, whose content may be as low as 93.6%.
Argon has approximately the same solubility in water as oxygen and is 2.5 times more soluble in water than nitrogen. Argon is colorless, odorless, nonflammable and nontoxic as a solid, liquid or gas. Argon is chemically inert under most conditions and forms no confirmed stable compounds at room temperature.
Although argon is a noble gas, it can form some compounds under various extreme conditions. Argon fluorohydride (HArF), a compound of argon with fluorine and hydrogen that is stable below 17 K (−256.1 °C; −429.1 °F), has been demonstrated. Although the neutral ground-state chemical compounds of argon are presently limited to HArF, argon can form clathrates with water when atoms of argon are trapped in a lattice of water molecules. Ions, such as ArH+
, and excited-state complexes, such as ArF, have been demonstrated. Theoretical calculation predicts several more argon compounds that should be stable but have not yet been synthesized.
Argon (Greek ἀργόν, neuter singular form of ἀργός meaning "lazy" or "inactive"), is named in reference to its chemical inactivity. This chemical property of this first noble gas to be discovered impressed the namers. An unreactive gas was suspected to be a component of air by Henry Cavendish in 1785. Argon was first isolated from air in 1894 by Lord Rayleigh and Sir William Ramsay at University College London by removing oxygen, carbon dioxide, water, and nitrogen from a sample of clean air. They had determined that nitrogen produced from chemical compounds was 0.5% lighter than nitrogen from the atmosphere. The difference was slight, but it was important enough to attract their attention for many months. They concluded that there was another gas in the air mixed in with the nitrogen. Argon was also encountered in 1882 through independent research of H. F. Newall and W. N. Hartley. Each observed new lines in the emission spectrum of air that did not match known elements.
Until 1957, the symbol for argon was "A", but now is "Ar".
Argon constitutes 0.934% by volume and 1.288% by mass of the Earth's atmosphere, and air is the primary industrial source of purified argon products. Argon is isolated from air by fractionation, most commonly by cryogenic fractional distillation, a process that also produces purified nitrogen, oxygen, neon, krypton and xenon. The Earth's crust and seawater contain 1.2 ppm and 0.45 ppm of argon, respectively.
The main isotopes of argon found on Earth are 40
Ar (99.6%), 36
Ar (0.34%), and 38
Ar (0.06%). Naturally occurring 40
K, with a half-life of 1.25×109 years, decays to stable 40
Ar (11.2%) by electron capture or positron emission, and also to stable 40
Ca (88.8%) by beta decay. These properties and ratios are used to determine the age of rocks by K–Ar dating.
In the Earth's atmosphere, 39
Ar is made by cosmic ray activity, primarily by neutron capture of 40
Ar followed by two-neutron emission. In the subsurface environment, it is also produced through neutron capture by 39
K, followed by proton emission. 37
Ar is created from the neutron capture by 40
Ca followed by an alpha particle emission as a result of subsurface nuclear explosions. It has a half-life of 35 days.
Between locations in the Solar System, the isotopic composition of argon varies greatly. Where the major source of argon is the decay of 40
K in rocks, 40
Ar will be the dominant isotope, as it is on Earth. Argon produced directly by stellar nucleosynthesis, is dominated by the alpha-process nuclide 36
Ar. Correspondingly, solar argon contains 84.6% 36
Ar (according to solar wind measurements), and the ratio of the three isotopes 36Ar : 38Ar : 40Ar in the atmospheres of the outer planets is 8400 : 1600 : 1. This contrasts with the low abundance of primordial 36
Ar in Earth's atmosphere, which is only 31.5 ppmv (= 9340 ppmv × 0.337%), comparable with that of neon (18.18 ppmv) on Earth and with interplanetary gasses, measured by probes.
The predominance of radiogenic 40
Ar is the reason the standard atomic weight of terrestrial argon is greater than that of the next element, potassium, a fact that was puzzling when argon was discovered. Mendeleev positioned the elements on his periodic table in order of atomic weight, but the inertness of argon suggested a placement before the reactive alkali metal. Henry Moseley later solved this problem by showing that the periodic table is actually arranged in order of atomic number (see History of the periodic table).
Argon's complete octet of electrons indicates full s and p subshells. This full valence shell makes argon very stable and extremely resistant to bonding with other elements. Before 1962, argon and the other noble gases were considered to be chemically inert and unable to form compounds; however, compounds of the heavier noble gases have since been synthesized. The first argon compound with tungsten pentacarbonyl, W(CO)5Ar, was isolated in 1975. However it was not widely recognised at that time. In August 2000, another argon compound, argon fluorohydride (HArF), was formed by researchers at the University of Helsinki, by shining ultraviolet light onto frozen argon containing a small amount of hydrogen fluoride with caesium iodide. This discovery caused the recognition that argon could form weakly bound compounds, even though it was not the first. It is stable up to 17 kelvins (−256 °C). The metastable ArCF2+
2 dication, which is valence-isoelectronic with carbonyl fluoride and phosgene, was observed in 2010. Argon-36, in the form of argon hydride (argonium) ions, has been detected in interstellar medium associated with the Crab Nebula supernova; this was the first noble-gas molecule detected in outer space.
Solid argon hydride (Ar(H2)2) has the same crystal structure as the MgZn2 Laves phase. It forms at pressures between 4.3 and 220 GPa, though Raman measurements suggest that the H2 molecules in Ar(H2)2 dissociate above 175 GPa.
Argon is produced industrially by the fractional distillation of liquid air in a cryogenic air separation unit; a process that separates liquid nitrogen, which boils at 77.3 K, from argon, which boils at 87.3 K, and liquid oxygen, which boils at 90.2 K. About 700,000 tonnes of argon are produced worldwide every year.
40Ar, the most abundant isotope of argon, is produced by the decay of 40K with a half-life of 1.25×109 years by electron capture or positron emission. Because of this, it is used in potassium–argon dating to determine the age of rocks.
Argon has several desirable properties:
Other noble gases would be equally suitable for most of these applications, but argon is by far the cheapest. Argon is inexpensive, since it occurs naturally in air and is readily obtained as a byproduct of cryogenic air separation in the production of liquid oxygen and liquid nitrogen: the primary constituents of air are used on a large industrial scale. The other noble gases (except helium) are produced this way as well, but argon is the most plentiful by far. The bulk of argon applications arise simply because it is inert and relatively cheap.
Argon is used in some high-temperature industrial processes where ordinarily non-reactive substances become reactive. For example, an argon atmosphere is used in graphite electric furnaces to prevent the graphite from burning.
For some of these processes, the presence of nitrogen or oxygen gases might cause defects within the material. Argon is used in some types of arc welding such as gas metal arc welding and gas tungsten arc welding, as well as in the processing of titanium and other reactive elements. An argon atmosphere is also used for growing crystals of silicon and germanium.
Argon is used in the poultry industry to asphyxiate birds, either for mass culling following disease outbreaks, or as a means of slaughter more humane than the electric bath. Argon is denser than air and displaces oxygen close to the ground during gassing. Its non-reactive nature makes it suitable in a food product, and since it replaces oxygen within the dead bird, argon also enhances shelf life.
Liquid argon is used as the target for neutrino experiments and direct dark matter searches. The interaction between the hypothetical WIMPs and an argon nucleus produces scintillation light that is detected by photomultiplier tubes. Two-phase detectors containing argon gas are used to detect the ionized electrons produced during the WIMP–nucleus scattering. As with most other liquefied noble gases, argon has a high scintillation light yield (about 51 photons/keV), is transparent to its own scintillation light, and is relatively easy to purify. Compared to xenon, argon is cheaper and has a distinct scintillation time profile, which allows the separation of electronic recoils from nuclear recoils. On the other hand, its intrinsic beta-ray background is larger due to 39
Ar contamination, unless one uses argon from underground sources, which has much less 39
Ar contamination. Most of the argon in the Earth's atmosphere was produced by electron capture of long-lived 40
K + e− → 40
Ar + ν) present in natural potassium within the Earth. The 39
Ar activity in the atmosphere is maintained by cosmogenic production through the knockout reaction 40
Ar and similar reactions. The half-life of 39
Ar is only 269 years. As a result, the underground Ar, shielded by rock and water, has much less 39
Ar contamination. Dark-matter detectors currently operating with liquid argon include DarkSide, WArP, ArDM, microCLEAN and DEAP. Neutrino experiments include ICARUS and MicroBooNE, both of which use high-purity liquid argon in a time projection chamber for fine grained three-dimensional imaging of neutrino interactions.
Argon is used to displace oxygen- and moisture-containing air in packaging material to extend the shelf-lives of the contents (argon has the European food additive code E938). Aerial oxidation, hydrolysis, and other chemical reactions that degrade the products are retarded or prevented entirely. High-purity chemicals and pharmaceuticals are sometimes packed and sealed in argon.
In winemaking, argon is used in a variety of activities to provide a barrier against oxygen at the liquid surface, which can spoil wine by fueling both microbial metabolism (as with acetic acid bacteria) and standard redox chemistry.
Since 2002, the American National Archives stores important national documents such as the Declaration of Independence and the Constitution within argon-filled cases to inhibit their degradation. Argon is preferable to the helium that had been used in the preceding five decades, because helium gas escapes through the intermolecular pores in most containers and must be regularly replaced.
Argon may be used as the carrier gas in gas chromatography and in electrospray ionization mass spectrometry; it is the gas of choice for the plasma used in ICP spectroscopy. Argon is preferred for the sputter coating of specimens for scanning electron microscopy. Argon gas is also commonly used for sputter deposition of thin films as in microelectronics and for wafer cleaning in microfabrication.
Cryosurgery procedures such as cryoablation use liquid argon to destroy tissue such as cancer cells. It is used in a procedure called "argon-enhanced coagulation", a form of argon plasma beam electrosurgery. The procedure carries a risk of producing gas embolism and has resulted in the death of at least one patient.
Incandescent lights are filled with argon, to preserve the filaments at high temperature from oxidation. It is used for the specific way it ionizes and emits light, such as in plasma globes and calorimetry in experimental particle physics. Gas-discharge lamps filled with pure argon provide lilac/violet light; with argon and some mercury, blue light. Argon is also used for blue and green argon-ion lasers.
Argon is used as a propellant in the development of the Variable Specific Impulse Magnetoplasma Rocket (VASIMR). Compressed argon gas is allowed to expand, to cool the seeker heads of some versions of the AIM-9 Sidewinder missile and other missiles that use cooled thermal seeker heads. The gas is stored at high pressure.
Argon-39, with a half-life of 269 years, has been used for a number of applications, primarily ice core and ground water dating. Also, potassium–argon dating and related argon-argon dating is used to date sedimentary, metamorphic, and igneous rocks.
Argon has been used by athletes as a doping agent to simulate hypoxic conditions. In 2014, the World Anti-Doping Agency (WADA) added argon and xenon to the list of prohibited substances and methods, although at this time there is no reliable test for abuse.
Although argon is non-toxic, it is 38% denser than air and therefore considered a dangerous asphyxiant in closed areas. It is difficult to detect because it is colorless, odorless, and tasteless. A 1994 incident, in which a man was asphyxiated after entering an argon-filled section of oil pipe under construction in Alaska, highlights the dangers of argon tank leakage in confined spaces and emphasizes the need for proper use, storage and handling.
Argon fluorohydride (systematically named fluoridohydridoargon) or argon hydrofluoride is an inorganic compound with the chemical formula HArF (also written ArHF). It is a compound of the chemical element argon.Argonium
Argonium, an ion combining a proton and an argon atom (and so also called protonated argon), (ArH+) can be made in an electric discharge, and was the first noble gas molecular ion to be found in interstellar space.Argon–argon dating
Argon–argon (or 40Ar/39Ar) dating is a radiometric dating method invented to supersede potassium-argon (K/Ar) dating in accuracy. The older method required splitting samples into two for separate potassium and argon measurements, while the newer method requires only one rock fragment or mineral grain and uses a single measurement of argon isotopes. 40Ar/39Ar dating relies on neutron irradiation from a nuclear reactor to convert a stable form of potassium (39K) into the radioactive 39Ar. As long as a standard of known age is co-irradiated with unknown samples, it is possible to use a single measurement of argon isotopes to calculate the 40K/40Ar* ratio, and thus to calculate the age of the unknown sample. 40Ar* refers to the radiogenic 40Ar, i.e. the 40Ar produced from radioactive decay of 40K. 40Ar* does not include atmospheric argon adsorbed to the surface or inherited through diffusion and its calculated value is derived from measuring the 36Ar (which is assumed to be of atmospheric origin) and assuming that 40Ar is found in a constant ratio to 36Ar in atmospheric gases.Bora–Hansgrohe
Bora–Hansgrohe (UCI Code: BOH) is a UCI WorldTeam cycling team established in 2010 with a German license, founded and managed by w:de:Ralph Denk. It is sponsored by BORA, German manufacturer, and Hansgrohe, bathroom fittings manufacturer. Its aim is "improving the image of road cycling in Germany".DEAP
DEAP (Dark Matter Experiment using Argon Pulse-shape) is a direct dark matter search experiment using liquid argon as target material. DEAP utilizes background discrimination based on the characteristic scintillation pulse-shape in argon. A first-generation detector (DEAP-1) with a 7 kg target mass operated at Queen's University to test the available pulse-shape discrimination at low recoil energies in liquid argon, and was moved to SNOLAB in October 2007 and ran into 2011. Discrimination of beta and gamma events from nuclear recoils in the energy region of interest (near 20 keV of electron energy) is required to be better than 1 in 108 to sufficiently suppress backgrounds in the DEAP-1 detector.
DEAP-3600 with 3600 kg of active mass is planned for operation beginning in mid 2015, with sensitivity to WIMP-nucleon scattering cross-sections as low as 10−46 cm² at 100 GeV.
A later 50 ton-scale detector (DEAP-50T) is planned.Igneous petrology
Igneous petrology is the study of igneous rocks—those that are formed from magma. As a branch of geology, igneous petrology is closely related to volcanology, tectonophysics, and petrology in general. The modern study of igneous rocks utilizes a number of techniques, some of them developed in the fields of chemistry, physics, or other earth sciences. Petrography, crystallography, and isotopic studies are common methods used in igneous petrology.Inductively coupled plasma mass spectrometry
Inductively coupled plasma mass spectrometry (ICP-MS) is a type of mass spectrometry which is capable of detecting metals and several non-metals at concentrations as low as one part in 1015 (part per quadrillion, ppq) on non-interfered low-background isotopes. This is achieved by ionizing the sample with inductively coupled plasma and then using a mass spectrometer to separate and quantify those ions.
Compared to atomic absorption spectroscopy, ICP-MS has greater speed, precision, and sensitivity. However, compared with other types of mass spectrometry, such as thermal ionization mass spectrometry (TIMS) and glow discharge mass spectrometry (GD-MS), ICP-MS introduces many interfering species: argon from the plasma, component gases of air that leak through the cone orifices, and contamination from glassware and the cones.
The variety of applications exceeds that of inductively coupled plasma atomic emission spectroscopy and includes isotopic speciation. Due to possible applications in nuclear technologies, ICP-MS hardware is a subject for special exporting regulations.Inert gas
An inert gas is a gas which does not undergo chemical reactions under a set of given conditions. The noble gases often do not react with many
substances, and were historically referred to as the inert gases. Inert gases are used generally to avoid unwanted chemical reactions degrading a sample. These undesirable chemical reactions are often oxidation and hydrolysis reactions with the oxygen and moisture in air. The term inert gas is context-dependent because several of the noble gases can be made to react under certain conditions.
Purified argon and nitrogen gases are most commonly used as inert gases due to their high natural abundance (78.2% N2, 1% Ar in air) and low relative cost.
Unlike noble gases, an inert gas is not necessarily elemental and is often a compound gas. Like the noble gases the tendency for non-reactivity is due to the valence, the outermost electron shell, being complete in all the inert gases. This is a tendency, not a rule, as noble gases and other "inert" gases can react to form compounds.Some name of inert gases are (1)Helium,(2)Radon,(3)Neon
(4)Argon (5)XenonIon laser
An ion laser is a gas laser that uses an ionized gas as its lasing medium.
Like other gas lasers, ion lasers feature a sealed cavity containing the laser medium and mirrors forming a Fabry–Pérot resonator. Unlike helium–neon lasers, the energy level transitions that contribute to laser action come from ions. Because of the large amount of energy required to excite the ionic transitions used in ion lasers, the required current is much greater, and as a result all but the smallest ion lasers are water-cooled. A small air-cooled ion laser might produce, for example, 130 milliwatts of output light with a tube current of about 10 amperes and a voltage of 105 volts. Since one ampere times one volt is one watt, this is an electrical power input of about one kilowatt. Subtracting the (desirable) light output of 130 mW from power input, this leaves the large amount of waste heat of nearly one kW. This has to be dissipated by the cooling system. In other words, the power efficiency is very low.Isotopes of argon
Argon (18Ar) has 25 known isotopes, from 30Ar to 54Ar and 1 isomer (32mAr), of which three are stable (36Ar, 38Ar, and 40Ar). On the Earth, 40Ar makes up 99.6% of natural argon. The longest-lived radioactive isotopes are 39Ar with a half-life of 269 years, 42Ar with a half-life of 32.9 years, and 37Ar with a half-life of 35.04 days. All other isotopes have half-lives of less than two hours, and most less than one minute. The least stable is 30Ar with a half-life shorter than 20 nanoseconds.
The naturally occurring 40K, with a half-life of 1.248×109 years, decays to stable 40Ar by electron capture (10.72%) and by positron emission (0.001%), and also transforms to stable 40Ca via beta decay (89.28%). These properties and ratios are used to determine the age of rocks through potassium–argon dating.Despite the trapping of 40Ar in many rocks, it can be released by melting, grinding, and diffusion. Almost all of the argon in the Earth's atmosphere is the product of 40K decay, since 99.6% of Earth atmospheric argon is 40Ar, whereas in the Sun and presumably in primordial star-forming clouds, argon consists of < 15% 38Ar and mostly (85%) 36Ar. Similarly, the ratio of the three isotopes 36Ar:38Ar:40Ar in the atmospheres of the outer planets is measured to be 8400:1600:1.In the Earth's atmosphere, radioactive 39Ar (half-life 269 years) is made by cosmic ray activity, primarily from 40Ar. In the subsurface environment, it is also produced through neutron capture by 39K or alpha emission by calcium. The content of 39Ar in natural argon is measured to be of (8.0±0.6)×10−16 g/g, or (1.01±0.08) Bq/kg of 36, 38, 40Ar. The content of 42Ar (half-life 33 years) in the Earth's atmosphere is lower than 6×10−21 parts per part of 36, 38, 40Ar. Many endeavors require argon depleted in the cosmogenic isotopes, known as depleted argon. In December 2013, 36Ar, in the form of argon hydride, was found in cosmic dust associated with the Crab Nebula supernova. This was the first time a noble molecule was detected in outer space.Radioactive 37Ar is a synthetic radionuclide that is created from the neutron capture by 40Ca followed by an alpha particle emission as a result of subsurface nuclear explosions. It has a half-life of 35 days.KH-5 Argon
KH-5 ARGON was a series of reconnaissance satellites produced by the United States from February 1961 to August 1964. The KH-5 operated similarly to the Corona series of satellites, as it ejected a canister of photographic film. At least 12 missions were attempted, but at least 7 resulted in failure. The satellite was manufactured by Lockheed. Launches used Thor-Agena rockets flying from Vandenberg Air Force Base, with the payload being integrated into the Agena.K–Ar dating
Potassium–argon dating, abbreviated K–Ar dating, is a radiometric dating method used in geochronology and archaeology. It is based on measurement of the product of the radioactive decay of an isotope of potassium (K) into argon (Ar). Potassium is a common element found in many materials, such as micas, clay minerals, tephra, and evaporites. In these materials, the decay product 40Ar is able to escape the liquid (molten) rock, but starts to accumulate when the rock solidifies (recrystallizes). The amount of argon sublimation that occurs is a function of the purity of the sample, the composition of the mother material, and a number of other factors. These factors introduce error limits on the upper and lower bounds of dating, so that final determination of age is reliant on the environmental factors during formation, melting, and exposure to decreased pressure and/or open-air. Time since recrystallization is calculated by measuring the ratio of the amount of 40Ar accumulated to the amount of 40K remaining. The long half-life of 40K allows the method to be used to calculate the absolute age of samples older than a few thousand years.The quickly cooled lavas that make nearly ideal samples for K–Ar dating also preserve a record of the direction and intensity of the local magnetic field as the sample cooled past the Curie temperature of iron. The geomagnetic polarity time scale was calibrated largely using K–Ar dating.Noble gas
The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a group of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low chemical reactivity. The six noble gases that occur naturally are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the radioactive radon (Rn). These elements are all nonmetals. Oganesson (Og) is variously predicted to be a noble gas as well or to break the trend due to relativistic effects; its chemistry has not yet been investigated.
For the first six periods of the periodic table, the noble gases are exactly the members of group 18. Noble gases are typically highly unreactive except when under particular extreme conditions. The inertness of noble gases makes them very suitable in applications where reactions are not wanted. For example, argon is used in incandescent lamps to prevent the hot tungsten filament from oxidizing; also, helium is used in breathing gas by deep-sea divers to prevent oxygen, nitrogen and carbon dioxide (hypercapnia) toxicity.
The properties of the noble gases can be well explained by modern theories of atomic structure: their outer shell of valence electrons is considered to be "full", giving them little tendency to participate in chemical reactions, and it has been possible to prepare only a few hundred noble gas compounds. The melting and boiling points for a given noble gas are close together, differing by less than 10 °C (18 °F); that is, they are liquids over only a small temperature range.
Neon, argon, krypton, and xenon are obtained from air in an air separation unit using the methods of liquefaction of gases and fractional distillation. Helium is sourced from natural gas fields that have high concentrations of helium in the natural gas, using cryogenic gas separation techniques, and radon is usually isolated from the radioactive decay of dissolved radium, thorium, or uranium compounds (since those compounds give off alpha particles). Noble gases have several important applications in industries such as lighting, welding, and space exploration. A helium-oxygen breathing gas is often used by deep-sea divers at depths of seawater over 55 m (180 ft) to keep the diver from experiencing oxygen toxemia, the lethal effect of high-pressure oxygen, nitrogen narcosis, the distracting narcotic effect of the nitrogen in air beyond this partial-pressure threshold, and carbon dioxide poisoning (hypercapnia), the panic-inducing effect of excessive carbon dioxide in the bloodstream. After the risks caused by the flammability of hydrogen became apparent, it was replaced with helium in blimps and balloons.Period 3 element
A period 3 element is one of the chemical elements in the third row (or period) of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when the periodic table skips a row and a chemical behaviour begins to repeat, meaning that elements with similar behavior fall into the same vertical columns. The third period contains eight elements: sodium, magnesium, aluminium, silicon, phosphorus, sulfur, chlorine, and argon. The first two, sodium and magnesium, are members of the s-block of the periodic table, while the others are members of the p-block. Note that there is a 3d subshell, but it is not filled until period 4, such giving the period table its characteristic shape of "two rows at a time". All of the period 3 elements occur in nature and have at least one stable isotope.Potassium-40
Potassium-40 (40K) is a radioactive isotope of potassium which has a very long half-life of 1.251×109 years. It makes up 0.012% (120 ppm) of the total amount of potassium found in nature.
Potassium-40 is a rare example of an isotope that undergoes both types of beta decay. About 89.28% of the time, it decays to calcium-40 (40Ca) with emission of a beta particle (β−, an electron) with a maximum energy of 1.31 MeV and an antineutrino. About 10.72% of the time it decays to argon-40 (40Ar) by electron capture, with the emission of a 1.460 MeV gamma ray and a neutrino. The radioactive decay of this particular isotope explains the large abundance of argon (nearly 1%) in the earth's atmosphere, as well as its abundance compared to 36Ar. Very rarely (0.001% of the time) it will decay to 40Ar by emitting a positron (β+) and a neutrino.SV Argon
Sport Vereniging Argon is a football and basketball club from Mijdrecht, Netherlands. Its male first football squad plays in the Hoofdklasse.Saint Martin crater
Saint Martin is an impact crater in Manitoba, Canada. It is located in the northern part of the Rural Municipality of Grahamdale, northwest of Lake St. Martin.
It is 40 km (25 mi) in diameter and its age was determined to be 227.8 ± 1.1 million years (Carnian stage of the Triassic) using the argon-argon dating technique. The crater is well preserved but poorly exposed at the surface as the whole region is covered by glacial drift.Shielding gas
Shielding gases are inert or semi-inert gases that are commonly used in several welding processes, most notably gas metal arc welding and gas tungsten arc welding (GMAW and GTAW, more popularly known as MIG (Metal Inert Gas) and TIG (Tungsten Inert Gas), respectively). Their purpose is to protect the weld area from oxygen, and water vapour. Depending on the materials being welded, these atmospheric gases can reduce the quality of the weld or make the welding more difficult. Other arc welding processes use alternative methods of protecting the weld from the atmosphere as well – shielded metal arc welding, for example, uses an electrode covered in a flux that produces carbon dioxide when consumed, a semi-inert gas that is an acceptable shielding gas for welding steel.
Improper choice of a welding gas can lead to a porous and weak weld, or to excessive spatter; the latter, while not affecting the weld itself, causes loss of productivity due to the labor needed to remove the scattered drops.William Ramsay
Sir William Ramsay, (; 2 October 1852 – 23 July 1916) was a Scottish chemist who discovered the noble gases and received the Nobel Prize in Chemistry in 1904 "in recognition of his services in the discovery of the inert gaseous elements in air" (along with his collaborator, John William Strutt, 3rd Baron Rayleigh, who received the Nobel Prize in Physics that same year for their discovery of argon). After the two men identified argon, Ramsay investigated other atmospheric gases. His work in isolating argon, helium, neon, krypton and xenon led to the development of a new section of the periodic table.